1. Field of the Invention
The present invention relates to Hall Effect sensors, specifically to resistive coupled Hall Effect sensors.
2. Description of the Related Art
Computer science engineering has produced an ever increasing data processing requirement, demanding faster and denser random access memory to keep pace with improved CPU speed and output. Random access memory (RAM) for computers has typically been constructed from capacitors.
There have been attempts to provide RAM through magnetic elements. Magnetic elements enable the memory the advantage of being highly reliable, nonvolatile in the event of power loss, and an infinite lifetime under use. However, magnetic ferrite memory elements eventually were replaced by planar arrays of semiconductors; which is much less expensive to manufacture, quicker in operation and more compact in design. Some efforts have been made in using semi-conductors to utilize the Hall Effect in memory devices.
The Hall Effect is an electrostatic phenomenon whereby a conductor carrying an electric current perpendicular to an applied magnetic field develops a voltage gradient which is transverse to both the current and the magnetic field. This principle has been applied in many electromagnetic devices, including those devices to produce field effect transistors (FETs). Moreover, FETs have been used to create digital memory devices, such as a Hall Effect ferromagnetic non-volatile random access memory cell. A Hall Effect ferromagnetic non-volatile random access memory cell comprises a Hall Effect sensor adjacent to a ferromagnetic bit which is surrounded by a drive coil. The drive coil is electrically connected to a drive circuit, and when provided with an appropriate current creates a residual magnetic field in the ferromagnetic bit, the polarity of which determines the memory status of the cell.
The Hall Effect sensor is a transducer that varies its output voltage in response to changes in magnetic field density and/or polarity. Hall Effect sensors are used in proximity switching, positioning, speed detection, and current sensing applications. In its simplest form, the sensor operates as an analog transducer, directly returning a voltage. The voltage is proportional to the current flowing through the conductor, and the flux density or magnetic induction perpendicular to the conductor. With a known magnetic field, its distance from the Hall plate can be determined. Using groups of sensors, the relative position of the magnet can also be deduced. Electricity carried through a conductor will produce a magnetic field that varies with a current, and a Hall sensor can be used to measure the current without interrupting the circuit.
Innovations in computer science technology have moved toward faster, more reliable, and smaller memory storage devices that apply the Hall Effect. Some improvements have been made in the field. Examples include but are not limited to the references described below, which references are incorporated by reference herein:
U.S. Pat. No. 5,075,247, issued to Matthews, discloses a non-volatile, static magnetic memory device, whose operation is based on the Hall Effect. The device includes a magnetic patch which stores data in the form of a magnetic field, a semiconductor Hall bar and a pair of integrally-formed bipolar transistors used for amplifying and buffering the Hall voltage produced along the Hall bar. Current is forced to flow down the length of the Hall bar causing a Hall voltage to be developed in a direction transverse to the direction of both the magnetic field and the current. The bases of the bipolar transistors are ohmically coupled to the Hall bar to sense the Hall voltage—the polarity of which is representative of the stored information. A system of current carrying conductors is employed for writing data to individual magnetic patches.
U.S. Pat. No. 5,295,097, issued to Lienau, discloses a nonvolatile random access memory that is disclosed having a substrate carrying separate magnetically polarizable domains each surrounded by a full write loop member and arranged to penetrate the Hall channel of a dual drain FET with its residual magnetic field. The domains are organized in word rows and bit columns, are each written to by a single full write current through the surrounding loop member and each read by a comparator connected to the FET drains. The memory can be fabricated in a variety of forms.
U.S. Pat. No. 5,329,480, issued to Wu et al., discloses a nonvolatile magnetic random access memory that can be achieved by an array of magnet-Hall effect (M-H) elements. The storage function is realized with a rectangular thin-film ferromagnetic material having an in-plane, uniaxial anisotropy and inplane bipolar remanent magnetization states. The thin-film magnetic element is magnetized by a local applied field, whose direction is used to form either a “0” or “1” state. The element remains in the “0” or “1” state until a switching field is applied to change its state. The stored information is detected by a Hall-effect sensor which senses the fringing field from the magnetic storage element. The circuit design for addressing each cell includes transistor switches for providing a current of selected polarity to store a binary digit through a separate conductor overlying the magnetic element of the cell. To read out a stored binary digit, transistor switches are employed to provide a current through a row of Hall-effect sensors connected in series and enabling a differential voltage amplifier connected to all Hall-effect sensors of a column in series. To avoid read-out voltage errors due to shunt currents through resistive loads of the Hall-effect sensors of other cells in the same column, at least one transistor switch is provided between every pair of adjacent cells in every row which are not turned on except in the row of the selected cell.
U.S. Pat. No. 6,140,139, issued to Lienau et al., discloses a Hall Effect ferromagnetic non-volatile random access memory cell comprising a Hall effect sensor adjacent to a ferromagnetic bit which is surrounded by a drive coil. The coil is electrically connected to a drive circuit, and when provided with an appropriate current creates a residual magnetic field in the ferromagnetic bit, the polarity of which determines the memory status of the cell. The Hall Effect sensor is electrically connected via four conductors to a voltage source, ground, and two read sense comparator lines for comparing the voltage output to determine the memory status of the cell. The read and write circuits are arranged in a matrix of bit columns and byte rows. A method for manufacturing said Hall Effect ferromagnetic non-volatile random access memory cell.
U.S. Pat. No. 6,288,929, issued to Lienau, discloses a non-volatile RAM device that is disclosed which utilizes a plurality of ferromagnetic bits each surrounded by a coil of a write line for directing the remnant polarity thereof is disclosed. The direction of magnetic remnance in each bit is dictated by the direction of a current induced into write line. Further, a magneto sensor comprising a magneto resistor coupled to a pair of collectors that is placed approximate to each bit. The magneto resistor is coupled to a control circuit for receiving current. The current passing across magneto resistor is biased in a direction either right or left of the original current flow direction. The collectors are coupled to a pair of sense lines, which are in turn, coupled to a voltage differential amplifier. The collector in the direction of biased current flow, will receive a greater number of electrons than the other collector, and therefore have a greater negative charge. This voltage differential is conducted through the sense lines to the voltage differential amplifier, where it is amplified and detected.
U.S. Pat. No. 6,330,183, issued to Lienau, discloses a nonvolatile ferromagnetic RAM device which is capable of reading the data stored in each magnet quickly and efficiently utilizing a minimal number of components. Specifically there is a nonvolatile ferromagnetic RAM which is capable of reading the data stored in each magnetic bit. The ferromagnetic memory cell, comprising of a base that is oriented in a horizontal plane. There is also a bit, made of a ferromagnetic material, having: a height that is oriented perpendicular to the horizontal plane of the base, and a polarity that can be directed along the height. Additionally, there is a sense line, positioned proximate the bit sufficient to detect the directed polarity of the bit; and a write line, positioned proximate the bit sufficient to direct the polarity of the bit. Additionally, there is a detector, coupled to the sense line; and a sample drive line, positioned proximate the bit to transmit an electric pulse that will increase the directed polarity of the bit sufficient to induce a wave into the sense line that can be detected by the detector.
Other innovations in the art include U.S. Pat. Nos. 6,229,729, 6,266,267, 6,317,354, 6,545,908, 6,710,624, 6,711,069, 6,864,711, 6,873,546, 7,123,050, issued to Lienau; 4,791,604 issued to Lienau, et al; 6,341,080, issued to Lienau, et al; and 7,023,727 issued to Lienau, et al, each of which is incorporated herein by reference.
The inventions heretofore known suffer from a number of disadvantages which include being unreliable, inconsistent, slow, and expensive.
What is needed is a memory device that solves one or more of the problems described herein and/or one or more problems that may come to the attention of one skilled in the art upon becoming familiar with this specification.